u

• ulimit - set or report file size limit
• umask - get or set the file mode creation mask
• umount - unmount a file system
• umountall - unmount file systems
• unalias - remove alias definitions
• uname - return system name
• uncompress - expand compressed files
• unexpand - convert spaces to tabs
• uniq - report or filter out repeated lines in a file
• unset - unset values and attributes of variables and functions
• unzip - list, test and extract compressed files in a ZIP archive
• unzipsfx - self-extracting stub for prepending to ZIP archives
• usp - set POSIX control parameters dynamically
• uudecode - decode a binary file
• uuencode - encode a binary file
• uuname - list names of known systems